1. Field of the Invention
This invention relates generally to control devices for electric motors and more particularly to a device to control the operations of an electric motor-driven well pump under conditions of availability of the liquid to be pumped within the productivity limits of the well and also under conditions of the complete non-availability of the liquid to be pumped.
2. Description of the Prior Art
Pump control devices are known in which rate of flow from a pump is monitored, however, the control methods heretofore implemented have been complicated, expensive to manufacture and maintain and largely unreliable in operation. Most have incorporated a complicated arrangement of check valves, delay circuits and timing devices among other things for their operation. Many different control schemes have been employed in attempts to solve the problems presented. Most have either presented new problems or only partially solved the problems presented or both. Most of these devices have thus met special needs as presented by specific problems and have therefore served narrow purposes. These prior art devices, among other disadvantages, have failed to deliver available liquid in a well to a storage facility, have been unreliable and unpredictable in operation under continued use and have been expensive and complicated to manufacture. Some of these prior art devices have been described in the following listed patents that were brought to the attention of the applicant through a novelty search conducted in the U.S. Patent and Trademark Office.
______________________________________ U.S. Pat. No. Title Patentee and Date ______________________________________ 4,329,120 Pump Protector Apparatus Walters 5/11/82 3,091,179 Well Pumping Operation Echols, 5/28/63 Control System 3,299,817 Above Ground Liquid Walters et al 1/24/67 Level Control 3,148,622 Water System LeVan et al 9/15/64 4,180,374 Well Pump Protection Bristow 12/25/79 System 2,430,257 Motor Control Apparatus Teeson 11/4/47 2,275,066 Automatic Pump Controller Otterbourg 3/3/42 2,981,159 Fluid Flow Motor Control Payne II et al 4/25/61 3,963,375 Time Delayed Shut-Down Curtis 6/15/76 Circuit for Recirculation Pump ______________________________________
It would be a great advantage to the art to provide a well pump control to apply power and to run a pump motor continuously when liquid to be pumped is sufficiently available in the well.
Another great and related advantage would be found in the provision to withhold the application of power so as to shut off the pump motor whenever liquid to be pumped is not sufficiently available in the well within the predetermined limits of productivity of the well.
A still further beneficial advantage would be realized by the provision of means to enhance pressure changes in a liquid passage flow line by the insertion of a venturi or other restriction in the liquid passage flow line.
Yet another advantage would be the provision of means to test for the existence of either a condition of availability of liquid to be pumped or non-avabilability of that liquid.
Still another related advantage would be to operate the pumping device in response to the determination of availability or non-availability of liquid.
It would further be a great advantage to provide a control system that implements all of the above recited advantages in an economical, dependable and rugged device that maintains a high level of dependability and reliability under a wide range of operating conditions.